AS MITT ROMNEY tests the waters for a potential 2008 presidential run, he’ll be able to tap a vein of affluent, motivated, activist supporters with considerable political experience — the Church of Jesus Christ of Latter-day Saints (LDS), a/k/a the Mormons. The Romney family is to the Mormons what the Kennedys are to the Catholics. Mitt Romney’s father, George, a former CEO of American Motors and governor of Michigan, himself ran for president in 1968. Marion Romney, one of Mitt Romney’s cousins, was once a member of the LDS Church’s First Presidency, a triumvirate of the world’s three most powerful Mormons. And then, of course, there’s Mitt. A former venture capitalist and Mormon bishop, Romney unsuccessfully challenged Ted Kennedy in a 1994 Senate campaign and then rescued the 2002 Winter Olympics in Salt Lake City, Utah — the Vatican of Mormonism — from certain disaster before being elected governor here. Like John F. Kennedy, who played to the religious loyalty and ethnic insularity of his fellow Catholics, and Michael Dukakis, who appealed to Greek pride, Romney — if he runs — will surely look to his own religious base to give his campaign leverage and traction.

If there’s a moment that marks the beginning of the LDS ascendancy, it came in 1979, when right-wing Christian fundamentalist Jerry Falwell announced the formation of the Moral Majority, the anti-choice, anti-woman, anti-gay, pro-school-prayer group that reshaped American politics. In Falwell’s coalition, individual Mormons joined forces with Christian fundamentalists and conservative Catholics in an attempt to make American politics more godly. The oft-isolated LDS Church had finally found willing partners.

Today, the nation’s Mormon population is relatively small: there are 5.5 million in the United States, compared to 66 million Roman Catholics. But their ranks are tight — a distinct advantage when operating in a fractious and factionalized society. In 1972, George McGovern and his liberal backers used similar cohesion to gain brief control of the Democratic Party. The conservative takeover of the GOP is a bigger success story; today, the former right-wing insurgents have become the right-wing establishment. Now the voraciously ambitious Mitt Romney wants a place at the table, if not the lead chair. And Mormon solidarity — next to which standard conservative esprit de corps pales in comparison — may help him get it.

FOR A CRASH course in Mormon political power, consider the important role the LDS Church played in the defeat of the Equal Rights Amendment, which would have guaranteed women equal rights under the law. Passed by the House in 1971 and by the Senate in 1972, the ERA enjoyed widespread national support and seemed destined to succeed. By 1976, 34 states had ratified it; only four more were needed to make it part of the Constitution.

Then the Mormons got involved. In October 1976, the LDS Church’s First Presidency — consisting of the church’s three highest-ranking members — issued a formal statement opposing the ERA: the amendment, the First Presidency warned, might "stifle many God-given feminine instincts" and lead to an uptick in homosexual activity. This denunciation had a near-immediate impact in Idaho, home to a relatively large Mormon electorate. The Idaho legislature had previously given the ERA the requisite two-thirds approval, but this was undone by a January 1977 referendum in which a popular majority opposed the amendment.

Next, the LDS Church turned its focus to the state-level International Women’s Year (IWY) conferences taking place around the country. These gatherings had no formal role in the amendment process, but served as highly public barometers of female support for the ERA. As Mormon historian D. Michael Quinn recounts in a forthcoming anthology, God and Country: Politics in Utah (Signature Books), LDS women in numerous states worked to block pro-ERA resolutions atIWY conferences. The process was top-down, and controlled by the Church’s (male) leadership. In Hawaii, for example, Mormon women received these written instructions: "Report to Traditional Values Van, sign in, pick up dissent forms. Sit together. Stay together to vote. Ask Presidency for help if needed." At other state conferences, male Mormon coordinators staked out various rooms and informed their compatriots when a particular vote was pending; the Mormon women in attendance then rushed in to participate. This kind of discipline and cohesion allowed the Saints, as the Mormons call themselves, to dominate conferences in states where their total numbers were quite small. For example, Mormons represented about four percent of the total populations of Washington and Montana, but accounted for half or more of the women attending each state’s IWY gathering. And in both Washington and Montana, every proposed pro-ERA resolution was defeated.

In addition, under the guidance of Gordon Hinckley — then a special adviser to the First Presidency, and now the president of the LDS Church — Mormon-led civic groups were set up in a dozen states. Anti-ERA speakers were invited to speak in LDS Church buildings, and massive letter-writing campaigns were launched. Here, too, the Mormons’ limited numbers belied their ultimate effect: by one estimate, Saints generated 85 percent of the anti-ERA mail sent in Virginia, where they made up only one percent of the population. Ultimately, after a promising beginning, the ERA was defeated. And while it might be going too far to say the LDS Church killed it, it certainly put the amendment on life support. True, Mormons made common cause with conservative Catholics and Protestant fundamentalists in their battle against the ERA, a collaboration that paved the way for the political sector now broadlyknown as the religious right. But without the LDS Church’s timely intervention and efficient opposition, the amendment probably would have passed.

More recently, Mormons have devoted their political efficacy to the fight against gay marriage. In 1994, the First Presidency issued a formal statement opposing the marriage of same-sex couples. Soon after, fliers offering advice on how to create anti-gay-marriage PACs were distributed at Mormon congregations nationwide. In the mid ’90s, the LDS Church’s national headquarters tapped couples from Utah to participate in anti-gay-marriage endeavors outside the state, and gave hundreds of thousands of dollars to "traditional marriage" campaigns around the country. Meanwhile, local leaders used their wards (which are analogous to parishes) to coordinate anti-gay-marriage lobbying efforts. In 1996, for example, at every LDS chapel in Texas, meetings were held to urge Mormons to join the Coalition for Traditional Marriage, a Church-sponsored lobbying group. The necessary registration forms were provided in case they wished to do so on the spot.

This strategy came to fruition in California during the fight over Proposition 22, an initiative to ban gay marriage in that state. In the year before the election, LDS leaders mobilized local congregations to support the ban, formally asking California Mormons to raise money, knock on doors, send mailings, and staff phone banks. It worked. In 2000, California voters approved Proposition 22 by a 23-point margin.